The field of the present invention is apparatus and methods for producing heat exchange with a body fluid flowing through a body conduit of a patient.
Catheters such as central venous line catheters are typically used in ICU (intensive care unit) patients, particularly in those patients who have suffered a stroke or other brain traumatic event. Central venous line catheters are typically about 5 to 12 French in size and have a flexible multi-lumen elongate body extending 6 to 12 inches. They may be introduced through the subclavian or jugular veins, or through the femoral vein of the patient, serving to provide the caretaker with easy and convenient access to the patient""s central blood supply via the central venous system. In this manner general access to the central blood supply is gained, enabling, for example, delivery of drugs, infusion fluids or nutrition, along with the gathering of patient blood for blood gas analysis and the like.
In certain medical circumstances, such as in the case of a stroke patient or other brain trauma patient, it may be desirable to rapidly reduce the patient""s body temperature. For example, fever, which is common in neuro-ICU patients, may exacerbate detrimental effects in the brain. It may be desireable to reduce the body temperature of a patient having a fever to a normal body temperature.
In some cases such as but not limited to, cardiac surgery, beating heart surgery, coronary arterial bypass graft (CABG) procedure, acute myocardial infarction procedure, aneurysm procedure etc., it is sometimes considered desirable to reduce the patient""s body temperature below normal body temperature so that the patient experiences hypothermia. Many advantages of hypothermia are known. By way of example, it has been found desirable to lower the temperature of body tissue in order to reduce the metabolism of the body. This has been particularly desirable in surgical applications where the reduced metabolism has made it possible to more easily accommodate lengthy operative procedures. In cases of stroke and several other pathological conditions, hypothermia also reduces the permeability of the blood/brain barrier. It inhibits release of damaging neurotransmitters and also inhibits calcium-mediated effects. Hypothermia also inhibits brain edema and lowers intracranial pressure.
Conventional therapies to cool a patient include treatment with acetaminophen (Tylenol), cooling blankets, ice water bladder lavages, and ice baths. These approaches to cooling a patient require excessive cooling time and do not provide for precise control of patient cooling.
In other medical situations, it may be desirable to maintain the patient""s body at normothermia when the body""s metabolic tendency is to drift below normal temperature of about 98.6xc2x0 F. (37xc2x0 C.), or it may be desirable to raise the patient""s body temperature once it has drifted below normal back to normothermia. For example, a patient may suffer from unintended hypothermia and may need to be warmed to a normothermic temperature, e.g., 98.6xc2x0 F. (37xc2x0 C.). These results can be obtained by intravascular heating. The catheters disclosed herein may be used in connection with heating/cooling systems that are disclosed in U.S. Pat. Nos. 6,019,783 and 6,146,411 which are hereby incorporated by reference as if fully set forth herein. If the desire is to cool a hyperthermic patient as quickly as possible, the system""s heat exchange capacity should be set to its coldest temperature setting, for example a system bath temperature of about 0xc2x0 C. If the desire is to warm a hypothermic patient back to normothermia as quickly as possible, the system""s heat exchange capacity should be set to its hottest temperature setting, for example a system bath temperature of about 49xc2x0 C.
To minimize the number of incisions and catheter insertions into the patient""s body and cool or heat the patient relatively quickly and in a controlled fashion, a central venous catheter may be configured to include a cooling or a heating exchange capability.
By supplementing the known functions of a central venous line catheter with the function of cooling or warming the patient""s blood, a catheter may take advantage of existing access to the venous system using a single, relatively small incision, reducing the risk of additional complications. The access, typically through the subclavian, jugular or femoral veins, is to the central blood supply, via the central venous system, and is therefore particularly expedient, permitting efficient cooling or warming of a patient. The term central venous system generally relates to the portion of the venous system which returns blood to the right side of the heart, including the inferior and superior vena cava.
A catheter having one or more lumens may be inserted into a blood vessel of a patient to deliver medication, collect blood for analysis, and the like. A separate lumen may be provided for transporting a heat exchange fluid, e.g., cold, warm or hot water or saline. The fluid may circulate via the lumen and through a thin-walled inflated balloon formed on the surface of the catheter. The fluid exchanges heat with the blood in the blood vessel via the thin walls of the balloon. Outside the patient""s body, the fluid passes through a cooling or heating system to re-cool or re-heat the fluid. Such a catheter may lower or raise the temperature of the patient""s blood and, as described above, may thereby improve the patient""s medical condition.
It would be advantageous to provide a heat exchange catheter that maximizes intravascular cooling and heating without compromising physiological conditions, and facilitates access to the patient""s blood stream, thereby overcoming one or more problems associated with the related art.
The present invention is directed to a heat exchange catheter and method for its use. A heat exchange element is combined with an infusion lumen to provide efficient cooling (and/or heating) and access to the patient""s blood steam.
In a first separate aspect of the invention, a heat exchange catheter comprises a generally tubular elongate body defining lumens through which one or more fluids may flow, at least one heat exchange element disposed about an implantable portion of the catheter, and at least one inflation element disposed within the heat exchange element. A fluid fills the inflation element and the same or a different fluid circulates through the heat exchange element.
In a second separate aspect of the invention, a heat exchange catheter comprises a generally tubular elongate body defining an inflow lumen and an outflow lumen. The inflow lumen supplies heat exchange fluid to at least one heat exchange element disposed about an implantable portion of the catheter and at least one inflation element disposed within the heat exchange element. The heat exchange fluid exits the heat exchange element and flows into the outflow lumen such that fluid may circulate through the heat exchange element via the inflow lumen and outflow lumen.
In a third separate aspect of the invention, a heat exchange catheter comprises a generally tubular elongate body defining an inflow lumen, an outflow lumen and an inflation lumen. The inflow and outflow lumens circulate heat exchange fluid within at least one heat exchange element disposed about an implantable portion of the catheter. The inflation lumen supplies inflation fluid to at least one inflation element disposed within the heat exchange element.
In a fourth separate aspect of the invention, at least one inflation element is configured to promote mixing of the heat exchange fluid as it flows between the inflation element and the heat exchange element.
In a fifth separate aspect of the invention, the generally tubular elongate body further defines at least one infusion lumen that provides access to the central blood supply of the patient.
In a sixth separate aspect of the invention, a heat exchange catheter is provided with multiple infusion lumens (preferably three to five infusion lumens) with infusion ducts separated along the catheter at spaced intervals, such that the catheter may be used to simultaneously introduce various fluids, such as medications, into the patient at different points in the patient""s blood stream, so as to avoid mixing incompatible fluids in excessive concentrations.
In a seventh separate aspect of the invention, the elongate body further defines a guidewire lumen that accommodates a guidewire that may be used to assist insertion of the catheter.
In an eighth separate aspect of the invention, a heat exchange element and/or the elongate body has an irregular surface that promotes mixing of, or disturbs the flow of, heat exchange fluid as the fluid flows through the heat exchange element.
In a ninth separate aspect of the present invention, it is contemplated that combinations of the foregoing separate aspects may be incorporated into a single embodiment.
Therefore, it is an object of the present invention to provide an improved heat exchange catheter and a method for its use. Other and further objects and advantages will appear hereafter.